Biomarkers are cellular, biochemical or molecular alterations that can be easily and non-invasively measured in human tissues and are directly or indirectly in the pathway of disease. Over the past two decades, scientific research has repeatedly shown that ambient air particulate pollution, also known as particulate matter (PM), induces lung and systemic inflammation, as well as reductions in lung function and accelerated lung aging. The limited availability of biomarkers that reflect at-risk exposures and preclinical effects on lung function dramatically limits opportunities for effective targeted prevention. To address this gap, our long-term goal is to identify novel biomarkers that reflect environmental influences and predict the risk of impaired lung function. We will leverage recent experimental and clinical evidence on the roles of Extracellular Vesicles (EVs)-i.e., tiny membrane-bound vesicles actively released by human cells into the bloodstream-and of their bioactive cargo of microRNAs (miRNAs) as novel conveyors of inflammatory responses. Recent evidence from animal and human studies has shown that PM induces the release of EVs into the bloodstream from cells in the lung and other relevant tissues. In particular, PM exposure causes release of EV-encapsulated miRNAs, which are key bioactive molecules that can control the expression of genes in recipient cells. Yet to date, no data in large, well-phenotyped populations are available to address the potential roles of EVs as part of the paths linking PM exposure to its adverse effects on lung function. In this proposal, we exploit the unique nature of the Normative Aging Study (NAS) cohort (n=750) in which we have repeated collections of blood samples, exposure data and lung function measures in up to 7 visits conducted over 20+ years of follow up. All findings will be independently validated in KORA (n=750), a cohort remarkably similar to the NAS for study design, exposure levels, and participants' characteristics. We hypothesize that the number, size, and miRNA cargo of blood EVs are modified in response to short- and/or long-term exposures to ambient PM (Aim 1); and that the EV number, size, and miRNA cargo reflect reduced lung function at the time of blood sampling and/or over subsequent serial visits (Aim 2). We will use advanced statistical modeling to integrate a panel of inflammation markers in the paths linking exposure, EVs, and impaired lung function; we will establish and make publicly available a reference dataset on the tissue/cell type of origin of blood EVs and of their miRNAs; we will use this dataset to estimate the sources of EV- encapsulated miRNAs linking PM to impaired lung function (Exploratory Aim 3). Across all aims, we will use detailed characterization of PM chemical components to capture their emission sources. As we can leverage a wealth of extant, ready-to-use resources and data from the NAS and KORA cohorts, we will be able to cost- effectively recapitulate data from more than two decades of follow up over a single grant cycle.